The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.
This invention relates to a device for increasing the survivability of pilings in flowing water. More particularly, this invention provides hydrodynamic structure to reduce the drag load on pilings in flowing water.
Many, many commercial and military structures and facilities are located along the coasts of the United States and abroad, and piling supported oilrigs, observation platforms, and anchoring posts are dispersed in offshore waters. In addition, significant numbers of homes and military installations are found along shores, in harbors, and along flowing waterways. Many of these constructions are supported on pilings in order to keep them away from potentially rising floodwaters.
Structures built on pilings are designed to withstand the hydrodynamic forces that they are likely to encounter during their life cycle. Often these life cycle and design considerations revolve around what is known as the one-hundred-year flood or one-hundred-year storm. That is, the supporting piling foundation is built such that the protected structure is raised above the potential of the one-hundred-year flood or storm. The piling foundation is also made with sufficient strength to withstand the hydrodynamic forces that accompany rapidly moving water and wind about it. Unfortunately, as has been discovered during recent years, the one-hundred-year storm can strike at any time and can strike during consecutive periods of less than one hundred years. When such events occur, the design and strength of the piling foundations are tested to their limits and quite often fail.
The major cause of this failure is due to moving water and the tremendous hydrodynamic forces that this moving water places on the pilings that support various structures. During a hurricane or typhoon, for example, the height of the water may not be sufficient to impact with the raised structure. However, the force of the moving water impinging upon the piling system causes the pilings to shift and move or crack, under the tremendous hydrodynamic drag-load produced by the hydrodynamic flow of water on and around the pilings. To date the only solutions to this problem have been to use larger, longer and more expensive pilings and/or use exotic and expensive piling materials. Lateral bracing between pilings and grading berms across coastal and flood plane constructions have had only minimal success. These are the only known means that have been employed to reduce the hydrodynamic drag load on piling foundations.
Thus, in accordance with this inventive concept, a need has been recognized in the state of the art for a cost-effective means utilizing hydrodynamic principles to extend the useful life of pilings in flowing waters.
An object of the invention is to provide a load reduction device for pilings in flowing fluid.
Another object of the invention is to provide devices mounted on pilings and utilizing hydro-dynamic principles to reduce the load imposed by flowing fluid on the pilings.
Another object of the invention is to provide a bi-directionally tapered hydrodynamic foil device mounted on pilings to reduce the fluid load created by flowing fluid on the pilings by at least two hundred percent.
Another object of the invention is to provide a self-orienting device in flowing fluid requiring no external power source to reduce flow drag on pilings.
Another object of the invention is to provide bi-directionally tapered hydrodynamic foil devices capable of being retrofitted on pilings to reduce the load imposed by flowing fluid on the pilings.
Another object of the invention is to provide mass-produced, cost-effective, devices mounted on pilings to reduce the load created by flowing fluid.
Another object of the invention is to provide cost-effective light-weight, flow-reduction devices mounted on pilings using vane-guide structures as bearing surfaces to eliminate parts and maintenance otherwise required of conventional bearing structures.
Another object of the invention is to provide a load reduction device mounted on pilings having non-uniform external surfaces and other shapes than round.
Another object of the invention is to provide flow-reduction devices mounted on pilings formed in a variety of shapes, sizes, lengths and colors.
These and other objects of the invention will become more readily apparent from the ensuing specification when taken in conjunction with the appended claims.
Accordingly, the invention is a device to reduce load created by flowing fluid on a piling. A bi-directionally tapered hydrodynamic foil has a traverse tube sized to fit around a piling in a spaced-apart relationship, and has a tapered leading vane portion located on one side of the traverse tube and extending to diametrically opposed opposite sides of the tube. The hydrodynamic foil additionally is provided with a tapered trailing vane portion located on the opposite side of the traverse tube as the tapered leading vane, and the tapered leading vane portion has a leading edge. The tapered trailing vane portion has an extended tapered shape of greater lateral area than the tapered leading vane portion to orient the leading edge of the tapered leading vane portion into the direction of flow of fluid flowing on the piling. Upper and lower collars engage the piling and contact the traverse tube to support and guide the bi-directionally tapered hydrodynamic foil during rotation around a longitudinal axis of the piling.